Ferromagnetic shape memory alloys （FSMAs） such as NiMnGa, FePd and FePt are attractive as a new magnetic actuator material. They show a large magnetic-field-induced strain of 3% 9% due to the variant rearrangement. ...Ferromagnetic shape memory alloys （FSMAs） such as NiMnGa, FePd and FePt are attractive as a new magnetic actuator material. They show a large magnetic-field-induced strain of 3% 9% due to the variant rearrangement. Recently, the present authors have reported that in the Ni-Ga-Fe alloy the martensitic transformationfrom the B2 and/or the L21 structures into a seven-layer or five-layer modulated structure occurs upon cooling. In this alloy system, however, it is impossible to obtain a martensite phase at RT with a Curie temperature （TC） higher than 100 ℃. In this work,the effects of substitution of Co for Ni on the martensitic and magnetic transformations,crystal structures and phase equilibria in Ni-Ga-Fe alloys were studied.Ni-Ga-Fe-Co alloys were prepared by induction melting under an argon atmosphere.Small pieces of specimens were taken from the ingot and homogenized at 1433 K for 24 h followed by quenching in water. The obtained specimens were aged at 773 K for 24 h and then quenched. The compositions of each phase were determined by energy dispersion X-ray spectroscopy （EDX）. The martensitic transformation temperatures and TC were measured by differential scanning calorimetry （DSC） and vibrating sample magnetometer （VSM） measurement. The crystal structure of martensite phase was observed by X-ray diffractmeter （XRD） and transmission electron microscope （TEM）.The Curie temperature TC was increased with increasing Co content while the martensitic transformation temperature slightly decreased. In the Ni<sup>54-x Ga<sup>27 Fe<sup>19 Cox ,TC increases from 303 K to 408 K with increasing Co content from x=0 to x=6. The crystal structure of the martensite phase and the phase equiribria in the Ni-Fe-Ga-Co alloys will be also presented.展开更多
Shape memory alloys (SMAs) are well-known as high damping materials. Recently,we have reported that the Cu-Al-Mn SMAs show a high internal friction as well as the other SMAs such as Ni-Ti, Cu-Zn-Al SMAs. Since the Cu-...Shape memory alloys (SMAs) are well-known as high damping materials. Recently,we have reported that the Cu-Al-Mn SMAs show a high internal friction as well as the other SMAs such as Ni-Ti, Cu-Zn-Al SMAs. Since the Cu-Al-Mn-based SMAs possess an excellent cold-workability, a strong recrystallization texture can be formed by thermomechanical treatment. The present authors demonstrated that the texture control is considerably effective for improving the SM properties and especially, in the Cu-Al-Mn-Ni SMAs with a strong {112}<110> recrystallization texture, a large pseudoelastic (PE) of about 7% can be obtained. Such a texture control is expected to enhance the damping capacity in the Cu-Al-Mn-based SMAs as well as PE. In this study, the effect of texture on the internal friction in Cu-Al-Mn and Cu-Al-Mn-Ni SMAs was investigated by tensile testing mode of Dynamic Mechanical Spectrometer (DMS). In sheet specimens with the {112}<110> texture, value of dynamic damping tanφ depends on the loading direction and an excellent damping capacity of tanφ= 0.1 can be obtained at the rolling direction in the martensite phase condition. Moreover, these Cu-Al-Mn-based SMAs show a high tensile strength over 600 MPa in the martensite phase. The present Cu-Al-Mn-based SMAs should have a great potential as the damping materials.展开更多
文摘Ferromagnetic shape memory alloys （FSMAs） such as NiMnGa, FePd and FePt are attractive as a new magnetic actuator material. They show a large magnetic-field-induced strain of 3% 9% due to the variant rearrangement. Recently, the present authors have reported that in the Ni-Ga-Fe alloy the martensitic transformationfrom the B2 and/or the L21 structures into a seven-layer or five-layer modulated structure occurs upon cooling. In this alloy system, however, it is impossible to obtain a martensite phase at RT with a Curie temperature （TC） higher than 100 ℃. In this work,the effects of substitution of Co for Ni on the martensitic and magnetic transformations,crystal structures and phase equilibria in Ni-Ga-Fe alloys were studied.Ni-Ga-Fe-Co alloys were prepared by induction melting under an argon atmosphere.Small pieces of specimens were taken from the ingot and homogenized at 1433 K for 24 h followed by quenching in water. The obtained specimens were aged at 773 K for 24 h and then quenched. The compositions of each phase were determined by energy dispersion X-ray spectroscopy （EDX）. The martensitic transformation temperatures and TC were measured by differential scanning calorimetry （DSC） and vibrating sample magnetometer （VSM） measurement. The crystal structure of martensite phase was observed by X-ray diffractmeter （XRD） and transmission electron microscope （TEM）.The Curie temperature TC was increased with increasing Co content while the martensitic transformation temperature slightly decreased. In the Ni<sup>54-x Ga<sup>27 Fe<sup>19 Cox ,TC increases from 303 K to 408 K with increasing Co content from x=0 to x=6. The crystal structure of the martensite phase and the phase equiribria in the Ni-Fe-Ga-Co alloys will be also presented.
文摘Shape memory alloys (SMAs) are well-known as high damping materials. Recently,we have reported that the Cu-Al-Mn SMAs show a high internal friction as well as the other SMAs such as Ni-Ti, Cu-Zn-Al SMAs. Since the Cu-Al-Mn-based SMAs possess an excellent cold-workability, a strong recrystallization texture can be formed by thermomechanical treatment. The present authors demonstrated that the texture control is considerably effective for improving the SM properties and especially, in the Cu-Al-Mn-Ni SMAs with a strong {112}<110> recrystallization texture, a large pseudoelastic (PE) of about 7% can be obtained. Such a texture control is expected to enhance the damping capacity in the Cu-Al-Mn-based SMAs as well as PE. In this study, the effect of texture on the internal friction in Cu-Al-Mn and Cu-Al-Mn-Ni SMAs was investigated by tensile testing mode of Dynamic Mechanical Spectrometer (DMS). In sheet specimens with the {112}<110> texture, value of dynamic damping tanφ depends on the loading direction and an excellent damping capacity of tanφ= 0.1 can be obtained at the rolling direction in the martensite phase condition. Moreover, these Cu-Al-Mn-based SMAs show a high tensile strength over 600 MPa in the martensite phase. The present Cu-Al-Mn-based SMAs should have a great potential as the damping materials.
